Renewable power like wind and solar aren't able to meet the world's growing energy demands, Irish says, so people have to rethink nuclear energy.

"This is clean energy on a massive scale," he said.

Irish's company plans to develop a nuclear reactor in Canada in the next decade using molten salt rather than the solid nuclear fuel and highly pressurized water of conventional designs like the Candu reactor.

The new technology results in a reactor six times more efficient, producing a third the nuclear waste while improving the safety of the system, he says.

The idea of the liquefied salt reactors have been around since the early days of nuclear power, but they've never been developed commercially.

Terrestrial, which raised $10 million last month in its first major financing, says it's aiming to change that, with a design it says will be cost-competitive with fossil fuels.

"We're not looking to build a reactor in a laboratory," said Irish. "We're just taking a reactor design off the shelf, taking it out of national lab, and we're seeking to commercialize it."

Burnaby, B.C.,-based General Fusion also says it's also trying to develop nuclear energy, but it's not exactly using off-the-shelf technology.

The company, as the name suggests, is trying to build the world's first commercial fusion reactor, which releases energy by crushing atoms together. Today's reactors are based on fission, where atoms are instead split apart.

General Fusion has already raised $100 million from investors like Amazon.com founder Jeff Bezos and oilsands producer Cenovus Energy. But that's a pittance compared with the many billions of dollars governments are spending to try to build a successful fusion plant in France called Iter.

Michael Delage, General Fusion's vice president of technology and corporate strategy, predicts his company's practical approach will allow it to succeed with far less money.

The company's design involves 200 synchronized pistons hitting a plasma-filled metal sphere at once, sending a shock wave of force that concentrates enough energy in the centre of the ball to force the atoms together.

Delage says if anyone is successful with fusion research, it will fundamentally change the world by creating a vast new source of energy.

"It's a big, big impact, not just in terms of the economic win or the scale of the business, but impacting the energy industry and the world."

After some ambitious timelines came and went, General Fusion is no longer giving specific targets, saying only that success is years down the road.

Toronto-based Thorium Power Canada Inc. is also cautious about specific timing, but like Terrestrial, it's at least banking on proven, decades-old technology.

The company wants to develop nuclear reactors powered by solid pellets of thorium rather than uranium in a design Paul Hardy, Thorium's senior vice-president of business development, says would allow for smaller modular plants that would be cheaper than large-scale nuclear.

"Our cost base is now a third the cost of conventional uranium reactors, which puts us in the same sort of wheelhouse as natural gas, somewhat clean coal, or oil," said Hardy.

The company has been in talks to build small-scale reactors in Chile and Indonesia, countries without natural uranium supplies, while Hardy says governments like China, Japan and the U.S. are also investing in the technology.

Queen's University professor Richard Holt, who holds an industrial research chair in nuclear materials, cautions that implementing any of these nuclear options won't be easy.

As for salt reactors, Holt says: "Molten salts are nasty things to deal with in some ways, they're often very corrosive and so on."

Thorium, meantime, requires prodding to keep the reaction going, which, while making a nuclear meltdown less likely, also adds its own complications, Holt said.

And regarding fusion, the long-promised solution to the world's energy demands, Holt says it's been promised for decades but there's no sign of a breakthrough yet.

"It's a huge amount of technology involved and it's a long way in the future," said Holt.